Check out this dulled area in the hood that creates a margin following the black-out paint. It goes the whole length of the hood on both sides. Is this original? This is the original paint, but I have never seen this before:

I have seen it before. Especially on older original paint, and if you ever notice some newer ones also. (example dodge trk hoods and roofs) Its as tho the pigmet deteriates or even excessive rubbing and buffing over the years. Either way the finish is basically wearing thin.

Probably a buff job and they did not want to get into the black with the compound so they taped that area off. Could possibly be a respray from some damage to the front fender or the edge of the hood. As you indicated it was original paint, if you have had the car the entire time I would not question your information, but alot of things can happen in a cars life prior to acquiring it if you have not owned it since new. Just my .02 worth.

I'm thinking it would polish right out with a DA polisher, might try letting a good detail shop see what they can do. If the single stage paint is wore almost through, it probably wouldn't be enough to polish it out.